January 31, 2013
Great Arctic Cyclone Not The Culprit Behind Record Ice Loss
Lee Rannals for redOrbit.com — Your Universe Online
Researchers are disputing the theory that the culprit behind the historic sea ice minimum was "The Great Arctic Cyclone of August 2012."
Writing in the journal Geophysical Research Letters, University of Washington researchers found that the freak summer storm was actually not solely responsible for 2012's record low for Arctic sea ice, but that other factors were in play.
Jinlun Zhang, lead author of the paper, and colleagues performed the scientific equivalent of a forensic exam on the event, running computer simulations of last summer's weather and comparing them against a second scenario that was identical, except without the super storm.
After the simulation, the team found that the storm caused the sea ice to pass the previous record ten days earlier in August than it would have otherwise, but it only reduced the final September ice extent by nearly 60,000 square miles, which was less than a five percent difference.
The actual minimum ice extent was 18 percent less than the previous record, which was set back in 2007.
Previous theories about the cyclone's effect focused on winds breaking up the ice, or driving ice flows into areas of warmer water. Results from the study suggest that neither process actually led to much of an increase in melting. Instead, the storm only sped up a process already set in place.
The 2012 Arctic cyclone was the most powerful one ever seen during the month of August, and the 13th most powerful of all Arctic storms in over 30 years of satellite records. Axel Schweiger, a polar scientist in the Applied Physics Laboratory and co-author of the study, said the impact on the ice was obvious, but the question was whether the ice that went away would have melted off anyways because it was already thin to begin with.
Research has shown in the past that thin ice, and areas of open water, allow sunlight to filter down to the water below, causing a dense layer of ice that sits 65 feet down to gradually warm.
Once the cyclone swept over the drifting ice flows, underside ridges churned up the water and brought sun-warmed seawater to the ice's bottom edge. The researchers' simulations suggest that during the cyclone there was a quadrupling of melting, and that this was the biggest cause for doubling ice loss during the storm. Without the previous effect of the thin ice, mixed with the sun's rays, the cyclone wouldn't have had the same impact.
"There were a lot of ideas and questions about this which seemed quite plausible," Schweiger told redOrbit in an email. "Science is about following up on those questions in a systematic way. I think we provided a first step here."
Next, he said the team will ask the question of whether or not this process can contribute to ice melt in other situations.
"Will a thinning ice pick really be more vulnerable to storms in general or was this a rare event," he told redOrbit. "What would happen if the timing of the storm was different? Do we need to account for processes such as bigger waves breaking up ice floes in future model experiments."